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Development of Chemically Modified Electrodes and Their Applications in the Environmental and Biological

Author: LanGuoHua
Tutor: WeiWanZhi
School: Hunan University
Course: Analytical Chemistry
Keywords: Single-walled carbon nanotubes DNA Dopamine(DA) Ascorbic acid(AA) Chemically modified electrode DNA functionalized carbon nanotubes SAMs Polyaniline
CLC: X830
Type: Master's thesis
Year: 2010
Downloads: 143
Quote: 1
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Abstract


Analytical chemistry is very importan in the development of national economy, the progress of scientific and the role of technological and natural resources. It cross-penetration with chemistry, physics, biology and other basic disciplines.The research of basic disciplines and development of high scientific have to be support by the analytical. And in the electroanalytical chemistry. Based on different chemically modified electrodes chemical / biological sensor device is simple, cheap, fast response and high sensitivity characteristics, and thus subject to widespread attention. The paper carried out a series of studies that presents a new chemically modified electrode as chemical / biological sensors, and achieved some good results, the main research work of this paper as follows:1. A novel carbon nanotubes (CNTs) film-modified electrode was developed by controllable adsorption of the CNTs onto the monolayer of dodecylamine modified GCE based on hydrophobic forces. The electrochemical characteristics of the dodecylamine monolayer-modified GCE were examined by cyclic voltammetry and electrochemical impedance spectroscopy. Compared with the self-assembled monolayer of dodecanethiol-modified gold electrode, the prepared dodecylamine monolayer-modified GCE presented the smaller resistance and the higher capacitance. In addition, after SWCNTs were controllably adsorbed onto the both modified electrodes by hydrophobic forces, the dodecylamine monolayer-modified GCE showed a larger capacitance than that of bare GCE for its small resistance and good conductivity of CNTs, but the SAM of dodecanethiol-modified gold electrode was failed to achieve the same result. Furthermore, the proposed SWCNTs dodecylamine monolayer-modified GCE was successfully used to determine dopamine in the presence of ascorbic acid after the adsorption of ssDNA.2. DNA-SWCNTs/PANI composite film modified glassy carbon electrode was fabricated. Electrochemical behaviour was evaluated by means of electrochemical impedance spectrocpy (EIS) and cyclic voltammetry (CV). The electrochemical behavior of dopamine (DA) at the modified electrode in the presence of ascorbic acid (AA) was studied. It was found that DNA-SWCNTs/PANI composite film showed an obvious electrocatalytic activity for the oxidation of DA. The peak current was good proportional to the concentration of DA over the range 0.05-30×10-5 mol/L in 0.1 mol/L phosphate buffer solution (pH7.0). The modified electrode was used to detection sampale DA with a satisfactory result.3. A new type of DNA sensor was constructed based onπ-πconjugate force, the ssDNA modified to SWCNTs. The modified electrode was characterized by cyclic voltammetry and electrochemical impedance method. And the modified electrode was used to the detection of the Cu2+ with square wave stripping voltammeter. The results showed that there was a linear relationship between logarithm of the current and logarithm of the copper concentration in the range of 0-15μM, and the detection limit was0.2μM. The interferences of othermetal ions, such as Zn2+ and Pb2+, and results showed that thesemetal ions dont interferedwith the determination of copper ions.4. A L-cysteine/gold nanoparticle modifide gold electrode was prepared and its electrochemical behaviour was evaluated by means of electrochemical impedance spectrocpy (EIS) and cyclic voltammetry (CV). The modified electrod accelerates the response of redox of hydroquinone stably. The oxidation peak current is linearly changed with the concentration of hydroquinone at the midified electrode in the concentration range of 4×10"3-3×10-3mmol/L. The linear regression equation is ip (μA)=-0.056+1.137c(μmol/L), with correlation coefficient is 0.9961, detection Iimit=1.83×10-7mol/L, signal-to-noise ratio is 3.

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